Biochar effectively remediates Cd contamination in acidic or coarse- and medium-textured soils: A global meta-analysis

Multitask Deep Learning Enabling a Synergy for Cadmium and Methane Mitigation with Biochar Amendments in Paddy Soils

“…This is probably due to those abundant inorganic minerals (i.e., Ca 2+ , Na + , K + , and Mg 2+ ) in the ash can exchange ions with Cd 2+ , finally generating coprecipitation and complexes. , The pH of biochar (ranging from 7 to 8.5) is found negatively correlated with the SHAP value (Figure e), which may be attributed to the presence of abundant functional groups (e.g., −COOH and −OH) that can strongly complex and stabilize Cd ions in soils. ,, However, this correlation becomes rather poor for the biochar pH higher than 8.5 ( R 2 = 0.047; Figure e). The elemental composition of biochar determines the type and quantity of surface functional groups of biochar; for instance, a higher O content of biochar leads to more abundant functional groups (such as −COOH), which can promote the chemical adsorption of Cd on biochar. Nevertheless, our SHAP analysis suggests that these variables of elemental compositions are poorly correlated to η-Cd (Figures f and S5b–d), implying that the key factors determining Cd immobilization may be not dominated by physicochemical processes …”

“…41 Additionally, the pH of biochar is another critical characteristic positively associated with the physicochemical immobilization of Cd and also affects microbial activities for CH 4 production in paddy soils. 12,42 Figure 2d shows a mean pH value of 9.3 for a broad range of biochar from various sources (i.e., a range of 6.1−12.2), which is likely due to their high ash content (ranging from 2.4 to 55.3% with a mean value of 20.6%; Figure 2e) consisting of alkaline minerals such as phosphate and silicate. 12 In addition, our statistical analysis also reveals a mean specific surface area (SSA) of 88.9 m 2 /g for biochar (ranging from 1.0 to 429 m 2 /g; Figure 2f), statistically demonstrating that biochar possesses satisfactory sites for physicochemical adsorption with heavy metals and microbial growth.…”

“…12,42 Figure 2d shows a mean pH value of 9.3 for a broad range of biochar from various sources (i.e., a range of 6.1−12.2), which is likely due to their high ash content (ranging from 2.4 to 55.3% with a mean value of 20.6%; Figure 2e) consisting of alkaline minerals such as phosphate and silicate. 12 In addition, our statistical analysis also reveals a mean specific surface area (SSA) of 88.9 m 2 /g for biochar (ranging from 1.0 to 429 m 2 /g; Figure 2f), statistically demonstrating that biochar possesses satisfactory sites for physicochemical adsorption with heavy metals and microbial growth. 43 Soil properties also significantly determine the performance of biochar for Cd and CH 4 mitigation in soils.…”

“…40,57,59 However, this correlation becomes rather poor for the biochar pH higher than 8.5 (R 2 = 0.047; Figure 5e). The elemental composition of biochar determines the type and quantity of surface functional groups of biochar; 12 for instance, a higher O content of biochar leads to more abundant functional groups (such as −COOH), which can promote the chemical adsorption of Cd on biochar. Nevertheless, our SHAP analysis suggests that these variables of elemental compositions are poorly correlated to η-Cd (Figures 5f and S5b−d), implying that the key factors determining Cd immobilization may be not dominated by physicochemical processes.…”

Effects of stabilizing materials on soil Cd bioavailability, uptake, transport, and rice growth

“…Meanwhile, the biochar is effective for promoting plant growth and reducing Cd accumulation (Albert et al, 2021;Wang et al, 2022), showing that the 1% application rate of biochar reduced the Cd concentrations of rice grains by 29.3-35.2%. Biochar derived from different raw materials and produced under different conditions can affect the remediation efficiency of Cd-contaminated agricultural soils (El-Naggar et al, 2021;El-Naggar et al, 2022).…”